As hardly soluble gelling agents, gelatin and agar-agar are generally known. For dissolving gelatin in water, first gelatin powder or gelatin sheet must be swollen with water then the mixture of gelatin and water is heated. For dissolving agar-agar in water, on the other hand, the agar-agar must be heated in hot water and the temperature must be maintained at at least 80.degree. C. for a long time.
Under these circumstances, methods have been proposed and/or developed for improving the solubility of gelatin, and the results of the research conducted for this purpose have been reported.
Japanese Patent Publication No. 31,911/1973 and U.S. Pat. No. 3,362,830, for example, disclose methods including steps wherein gelatin powder is first dissolved in water together with an equivalent amount or more of sugars, then the solution thus obtained is dried by means of such methods as spray-drying, etc. On the other hand, Japanese Patent Disclosure No. 162,949/1980 discloses a method wherein water-containing gelatin is heated by use of microwaves to melt and dry it rapidly, then the dried gelatin is frozen and subsequently it is crushed into powder in the frozen condition.
According to the former method, however, a large amount of sugars must be used as the quality-improving agent, and moreover, the resulting gelatin powder is a mixed powder of gelatin and sugars. Therefore it cannot be said that these methods improve the quality of gelatin itself. The latter method, on the other hand, indispensably requires the steps of adding water for forming water-containing gelatin; drying for removing the water content previously added thereto; and crushing this dried gelatin in frozen condition, and thus the method is quite complicated.
On the other hand, no method for improving the solubility of agar-agar has been proposed or developed so far at all.